The present invention is concerned generally with a power gas burner system wherein the gas-primary air mixture is ignited before the mixture is introduced into the combustion chamber, and combustion is completed upon the introduction of turbulated secondary air into the combustion chamber. The present invention also is concerned with a multiplex power gas burner system having a plurality of segregated combustion chambers and a corresponding number of gas burners adapted for ignition by a single ignition source.
Gas burner systems provide means for mixing a gaseous fuel with a predetermined quantity of air, igniting the gas-air mixture, and combusting the gas-air mixture to release heat, which may be recovered by a heat exchanger. Two types of gas burners are generally known. In the first type, referred to as a secondary/primary power burner, a mixture of gas and a quantity of primary air are introduced into a combustion chamber, where the mixture is ignited. A supply of secondary air necessary to complete combustion of the gas is passed through a turbulator and introduced into the combustion chamber separately from the gas-primary air mixture. In the second type, referred to as a total premix burner, all of the air for combustion is mixed with the gas and passed through a fine-ported distribution head located within the combustion chamber. Ignition of the gas-air mixture takes place after the mixture exits the distribution head.
Each combustion chamber of the above-described burner systems requires a separate ignition source because ignition takes place within the combustion chamber. As a result, existing burner systems generally have large, complex combustion chambers with multiple heat exchanger passes, in order to minimize the number of ignition sources required. However, the complexity of the chambers offsets in part the savings associated with limiting the number of ignition sources, and the size of the chambers results in waste of heat exchanger surfaces when these burner systems are operated at reduced capacities.
In addition, the introduction of secondary air to existing burner systems prior to or at the same time as ignition renders these systems susceptible to variations in air flow. Both the ease of ignition and the stability of the burner flame generally decrease in existing burner systems as the secondary air flow rate increases. This characteristic limits the secondary air flow rates of these systems.
The operational range of a given burner system may be stated in terms of the gas turn-down ratio, i.e., the minimum gas flow rate expressed as a percentage of the maximum gas flow rate. For example, the gas turn-down ratio of a secondary/primary power system typically is approximately fifty percent whereas the gas turn-down ratio of a premix power burner system typically is only about ten percent. Existing burner systems, particularly those having large combustion chambers, may experience significant condensation and ignition problems even when they are operated in accordance with their respective gas turn-down ratios.
The gas burner system of the present invention comprises a burner and an opening in a combustion chamber aligned with the burner. A turbulator disk or plate may be arranged between the burner and the chamber opening. The turbulator disk defines a central port and a plurality of peripheral voids adjacent to the central port.
The burner communicates with both a gaseous fuel supply, such as natural gas, and an air supply. A portion of the air sufficient for ignition but not complete combustion of a predetermined quantity of gas, referred to as primary air, may be mixed with the gas. The balance of the air, referred to as secondary air, may travel past the burner toward the combustion chamber.
The gas-primary air mixture may be ignited at the burner to produce a burner flame. The burner flame and some of the secondary air may be directed through the central port of the turbulator disk into the combustion chamber. The remainder of the secondary air may be directed through the voids into the combustion chamber to provide highly turbulated air for combustion of the uncombusted gas from the gas-primary air mixture.
The burner system of the present invention may be applied to any gas fired appliance, and particularly to boilers, steam generators and water heaters. The invention, and the resultant high localized heat release associated therewith, may provide particular benefits when used in conjunction with water-backed heat exchangers. The burner system of the present invention also may be used with air-backed heat exchangers, provided that the operating conditions of the burner system are matched to the materials used in the heat exchangers to prevent the heat exchangers from being damaged by exposure to the high localized temperatures produced by the burner system.
The gas burner system of the present invention and many of its attendant advantages may be more readily understood in view of the following drawings and detailed description.